The semiconductor integrated circuit (IC) industry has experienced exponential growth over the last few decades. In the course of IC evolution, high voltage technology has been widely used in power management, regulators, battery protectors, DC motors, automotive circuits, panel display drivers, etc. On the other hand, low voltage technology is typically used for logic cores, microprocessors, and microcontrollers. Some modern IC designs integrate both high voltage and low voltage devices on a single chip.
In both high voltage and low-voltage technologies, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. One advancement implemented as technology nodes shrink, in some IC designs, has been the replacement of the typically polysilicon gate electrode with a metal gate electrode to improve device performance with the decreased feature sizes. Semiconductor devices of the replacement gate technology are integrated on the same chip with a logic core, which supports the logic core to accomplish an intended function and limits or eliminates the need for inter-chip communication. However, there are challenges to embed low voltage devices and high voltage devices on the same chip, especially on 28 nm node and beyond processes.